Movement (e.g., flexion and extension) of the natural human knee involves movements of the femur and the tibia. Specifically, during flexion and extension, the distal end of the femur and the proximal end of the tibia articulate relative to one another through a series of complex movements. Damage (e.g., trauma) or disease can deteriorate the bones, articular cartilage, and ligaments of the knee, which can ultimately affect the ability of the natural knee to function in such a manner. As a result, knee prostheses have been developed and implanted into surgically prepared ends of the femur and tibia.
A typical knee prosthesis for a total knee replacement, for example, includes a tibial component or tibial tray coupled to the patient's tibia, a femoral component coupled to the patient's femur, and a bearing component (or tibial insert) positioned between the tibial tray and the femoral component and including a bearing surface to accommodate the condyles of the femoral component. In some situations, it may be desirable that the tibial insert rotate relative to the tibial tray. Such rotation more closely replicates the motion of the patient's natural anatomy. In other cases, however, it may be desirable to prevent the tibial insert from rotating relative to the tibial tray. For example, various ligaments which support the knee may be compromised or damaged. In such a case, rotation of the tibial insert relative to the tibial tray may create an unstable knee. As such, a surgeon will decide on a case-by-case basis whether to use a rotating or non-rotating tibial assembly. This decision may be made pre-operatively or intra-operatively, for example. Additionally, it may be desirable to change a rotating tibial insert to a non-rotating tibial insert during a revision type surgery, for example.